The fuel tank does not vent through the small line leaving the top of the tank and going up front when filling at the station. You are pouring a lot of liquid into the tank, the same amount of air needs to come out. Problem is, this air needs to be diverted away from the fuel coming in or it will start splashing and gulping, causing the station filler gun to shut off.
I am not sure how they vented your particular tank. On the f150's, the earlier models they filled the fuel through the large filler hose, and they had a small corrugated plastic hose mounted at the top of the large hose inside to direct the air out and away from the fuel going in. This didn't work that great, and the smaller hose was famous for falling down inside the large hose causing filling problems on these trucks (1980-86).
Sometime around 1987 they changed things around and it worked much better. They mounted a smaller rubber hose to the fill spout, and this smaller rubber hose layed on the inside the larger rubber fill neck hose. The fuel from the station nozzle went down the smaller rubber hose, and the air came back up the large fill neck hose and vented through a slot in the fill neck. This system worked much better than the older style.
Not sure how they set up the rangers, but it's going to be along one of those themes above.